Mitochonic Acid-5 Inhibits Reactive Oxygen Species Production and Improves Human Chondrocyte Survival by Upregulating SIRT3-Mediated, Parkin-dependent Mitophagy

Abstract

Mitochondrial dysfunction is related to the pathogenesis of osteoarthritis (OA); however, there are no effective drugs to treat OA for maintaining mitochondrial homeostasis. Studies have shown that mitochonic acid-5 (MA-5) has a protective effect against mitochondrial damage and plays a role in mitophagy. However, it is not clear whether MA-5 has a beneficial effect on inflammatory articular cartilage. Here, human OA cartilage was obtained from patients undergoing total joint replacement. Interleukin-1β (IL-1β) was used to stimulate chondrocytes and induce inflammatory injury. Cell Counting Kit-8, TUNEL, and flow cytometry assays were used to assess apoptosis. Gene expression was examined using quantitative reverse transcription-polymerase chain reaction. Mitochondrial function was evaluated using immunoblotting, mitochondrial membrane potential assay, JC-1 staining, and immunofluorescence analysis. Mitophagy was detected using immunoblotting and immunofluorescence. 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP), a specific inhibitor of Sirtuin 3 (SIRT3), was used to block the SIRT3/Parkin pathway. Mitophagy in the cartilage sections was evaluated via immunohistochemistry. IL-1β was found to induce chondrocyte apoptosis by inhibiting SIRT3 expression and mitophagy. In addition, inflammatory damage reduced the mitochondrial membrane potential and promoted the production of intracellular reactive oxygen species (ROS), leading to increased mitochondrial division, mitochondrial fusion inhibition, and the consequent mitochondrial damage. In contrast, the MA-5 treatment inhibited excessive ROS production by upregulating mitophagy, maintaining the mitochondrial membrane potential, and reducing mitochondrial apoptosis. After chemically blocking SIRT3 with 3-TYP, Parkin-related mitophagy was also inhibited, an effect that was prevented by pretreatment of the chondrocytes with MA-5, thereby suggesting that SIRT3 is upstream of Parkin. Overall, MA-5 was found to enhance the activity of SIRT3, promote Parkin-dependent mitophagy, eliminate depolarized/damaged mitochondria in chondrocytes, and protect cartilage cells. In conclusion, MA-5 inhibits IL-1β-induced oxidative stress and protects chondrocytes by upregulating the SIRT3/Parkin-related autophagy signaling pathway.

Osthole Suppresses Knee Osteoarthritis Development by Enhancing Autophagy Activated via the AMPK/ULK1 Pathway

“…Therefore, the activation of LC3 II and concomitant decrease in p62 together signify an increase in autophagy. Previous studies have shown that the mitochondria and apoptosis change during the pathogenesis of KOA due to the decrease in autophagy [ 30 ]. In our study, osthole treatment increased the level of LC3 II and decreased the p62 level, which was accompanied by an increase in the number of Aps by TEM in vitro and in vivo.…”

A Promising Strategy to Treat Neurodegenerative Diseases by SIRT3 Activation

“…The adipokine omentin improves myocardial infarction-induced heart failure by activating mitophagy via the SIRT3/FOXO3 pathway [ 101 ]. Mitochonic acid-5 (MA-5) activates SIRT3 and promotes Parkin-dependent mitophagy in chondrocytes whereas 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP), a specific inhibitor of SIRT3, blocks the SIRT3/Parkin pathway [ 107 ]. Thus, SIRT3’s protective actions in several injury models involve mitochondrial quality control by mitophagy.…”

Decrease in UCP1 by sustained high lipid promotes NK cell necroptosis to exacerbate nonalcoholic liver fibrosis

“…5F), con rming the key role of c-Myc activation on regulating NK KO cell death. Furthermore, when an autophagy-stimulating reagent, mitochonic acid-5 (MA5) or valproic acid (VPA), was added to the PA-treated UCP1 −/− NK cells [31,32] , no obvious restoration in NK cell activities was found, as suggested by cell death, CD69, NKG2D, IFN-γ, and granzyme B (Figs. 5G and H; Supplementary Fig.…”